[Kali_Namir]

Often times, The Empress/Emperor are encircled by the signs of the zodiac, her by the actual symbol and him by the more earthly representations, so that could be one for Heaven's Monarch...

The Devil card sometimes represents enslavement/self-enslavement so maybe some form of chains/ball and chains somehow...it also used to be a representation of the pagan god Pan, so you might could work something in with that. You could also make the horns into a mask or hat and that would give a slightly different pose.

For the Pillar of the Sky one, you could always do a slightly closer tower that is crumbling.

Since The World card represents Victory and Triumph, you could possibly do something with a wreath of laurel leaves as a background or something of that such.

Those are just some ideas that I got after looking through my cards and their meanings and seeing what felt like it didn't get fully represented.